1. Field of the Invention
The present invention relates to a machine controller and more specifically to a machine controller that intercommunicates with and issues machining program commands to a plurality of peripherals.
2. Description of the Related Art
First, in this specification, “peripherals” include robots that conduct work such as a workpiece change, carriers that carry workpieces, tool changers, and the like, which operate at timing different from that of machining by a machine tool. “Work” refers to a sequence of operations performed by these peripherals for the machine tool for predetermined purposes.
A plurality of motors are attached to a machine tool and a peripheral, and these motors consume large amounts of power during operations such as positioning and axial movement. In a facility such as a factory in which a plurality of machine tools and peripherals are installed, if these motors operate at the same timing, the maximum power consumption in the entire facility may become larger, causing an overload on the power supply equipment in the facility. As a result, the maximum power consumption may exceed the power capacity of the power receiving equipment or private electric generator installed in the facility. If the maximum power consumption exceeds the power capacity, the voltage in the facility may drop, posing an obstacle to the operation of the facility.
To avoid such situations as a voltage drop in the facility, possible methods include the installation of power receiving equipment having a huge power capacity; however, when such power receiving equipment is used, a higher basic contract rate must be paid to an electric power company.
To address power consumption problems without installing power receiving equipment having a large power capacity, there is a need to control operations of industrial machines so that the maximum power consumption in the entire facility is reduced. Some examples of prior art techniques for responding to this need will be given below.
Japanese Patent Application Laid-Open No. 2010-176503 discloses a technique by which, when a machine tool machines a workpiece, the numerical controller for the machine tool transmits a pause command to a robot (peripheral), and the robot that receives the pause command pauses, thereby reducing the robot power consumption. This technique deals with only an issue of reduction in power consumption in a connection between a single machine tool and a robot in the vicinity of the machine tool, and does not aim to reduce power consumption in the whole of a facility in which a plurality of peripherals are placed around a machine tool.
Japanese Patent Application Laid-Open No. 2011-156598 discloses a technique by which, if the power consumption by a machine tool continues to exceed a prescribed value for a predetermined period of time, the controller for the machine tool decreases the feedrate for feed movement or the acceleration/deceleration for spindle rotation movement, thereby reducing the maximum power consumption. This technique controls the machine tool speed to reduce the power consumption. Therefore, productivity may be lowered due to prolonged machining time, or machining conditions may be changed due to a change in the feedrate or spindle rotation speed.
Japanese Patent Application Laid-Open No. 2011-121283 discloses a technique by which a plurality of injection molding machines are connected to a network, and the injection process schedule for a local machine is decided based on the injection process schedule for other machines in injection molding scheduling such that the maximum allowable power is not exceeded, thereby reducing the maximum power consumption. However, this technique controls the process schedules for injection molding machines to reduce the power consumption. Therefore, depending on the controlled process schedules, productivity may be lowered due to prolonged machining time.